"Although placebos have repeatedly been shown to increase physical performance and endurance, much less is known about the effect of their negative counterpart, nocebos. Here, we employ negative suggestions and a sham electrical stimulation as a nocebo conditioning procedure in healthy subjects performing a leg extension exercise to total exhaustion. Using two different protocols, we analyze the contribution of expectation alone or the combination of conditioning and expectation to the nocebo effect evaluated as the change of work performed and rate of perceived exertion. We find that it is possible to negatively modulate the physical performance in both cases, and we argue that this effect can effectively offset the outcome of training programs."

Implication. The effects of negative dispositions on athletic performance are strong enough to counteract physical training benefits. When preparing for important competitions it is important to prevent negative events (nocebos), prepare strategies that predict positive outcomes, and to present conditions that allow an athlete to feel very well on the day of competitions.